Bentonite is a rock primarily composed of clay minerals (very fine particles smaller than 2 micrometers). Geologically, bentonite is a clay layer rich in montmorillonite with other companions. It is important to note that bentonite is not a single mineral but a group of minerals that together form the bentonite rock. The formation environment of this rock includes shallow, low-energy water and a mild climate.
Key Component of Bentonite: Montmorillonite
The most important component of bentonite is the montmorillonite mineral group. The significant properties of montmorillonite minerals include ion exchange, plasticity, ionic expansion and contraction.
The characteristics of the smectite family of minerals depend on their chemical composition and structure. In sodium montmorillonite ions, the rate of ion absorption, plasticity, expansion, and contraction is higher than in calcium ions. The dimensions of the sodium and calcium montmorillonite networks naturally increase from 9.6 Angstroms to 20 Angstroms when the surrounding humidity reaches 100%.
Sodium montmorillonite absorbs and swells several times its original volume, transforming into a gel-like, plastic, and adhesive state, expanding up to 18 times its original size.
Important Minerals in Bentonite
Bentonite is a clay mineral primarily composed of smectite minerals, which are structured as a series of dioctahedral and trioctahedral layers. The dioctahedral minerals include montmorillonite, beidellite, and nontronite. Trioctahedral minerals include hectorite and saponite.
Bentonite types are briefly classified according to their various applications:
- Sodium Bentonite
- Calcium Bentonite
- Organic Bentonite
- Acid-Activated Bentonite
Each of these types of bentonite has specific properties suited for different industrial uses, such as in drilling fluids, cat litter, binder in foundry sands, and more.